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    <p><tt>Dear Jie Peng,</tt></p>
    <p><tt>   one way to set the temperature of your system in a MD simulation
        is by the use of the <br>
      </tt></p>
    <p><tt>   ion_temperature and tempw variable pair in the &IONS
        namelist</tt></p>
    <p><tt>   read the description of these variable in the input
        documentation ( <a class="moz-txt-link-freetext" href="http://www.quantum-espresso.org/Doc/INPUT_PW.htm">http://www.quantum-espresso.org/Doc/INPUT_PW.htm</a>
        )<br>
      </tt></p>
    <p><tt>   one thing that you can do is to start from, or close to,
        the equilibrium geometry and define ion_temperature = 'initial'
        setting tempw to twice the desired temperature.</tt></p>
    <p><tt>   the system will start at the potential energy minumum.
        after a little while the initial kinetic energy will
        redistribute among all the degrees of freedom (kinetic and
        potential-related ones) and the kinetic energy should oscillate
        roughly around the desired temperature.<br>
      </tt></p>
    <p><tt>   If you want to further modify the system temperature you
        can then play with other options of the ion_temperature
        variable.</tt></p>
    <p><tt>    best,<br>
      </tt></p>
    <p><tt>stefano</tt><br>
    </p>
    <br>
    <div class="moz-cite-prefix">On 14/04/2018 20:16, Jie Peng wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAJTOooHyXRcuHV17ZwmVkBvrEN3BY=e9HMV+mhaPwEvOOnbTdA@mail.gmail.com">
      <div dir="ltr">Stefano:
        <div><br>
        </div>
        <div>Thanks! This is so informative, and indeed I tried larger
          unit cells. But then I have another issue which is: the
          temperature never reach desired one. Below is what I did</div>
        <div><br>
        </div>
        <div>For a 2*2*2 supercell with input file:</div>
        <div><br>
        </div>
        <div>
          <div><i>&control</i></div>
          <div><i>    calculation='vc-cp',</i></div>
          <div><i>    title='Halfnium disulfide'</i></div>
          <div><i>    restart_mode='restart',</i></div>
          <div><i>    ndr=52,</i></div>
          <div><i>    ndw=53,</i></div>
          <div><i>    nstep=1200000,</i></div>
          <div><i>    iprint=10</i></div>
          <div><i>    isave=100,</i></div>
          <div><i>    tstress = .true.</i></div>
          <div><i>    tprnfor = .true.</i></div>
          <div><i>    dt=10,</i></div>
          <div><i>    wf_collect=.true.</i></div>
          <div><i>    etot_conv_thr=1e-6</i></div>
          <div><i>    forc_conv_thr=1e-3</i></div>
          <div><i>    ekin_conv_thr=1e-5</i></div>
          <div><i>    prefix='HfS2',</i></div>
          <div><i>    pseudo_dir='/home/jpeng/HfS2/potential'</i></div>
          <div><i>    outdir='./tmp/',</i></div>
          <div><i> /</i></div>
          <div><i> &system</i></div>
          <div><i>    ibrav= 4,</i></div>
          <div><i>    a=7.3058</i></div>
          <div><i>   c=11.3088</i></div>
          <div><i>    nat=24, ntyp= 2,</i></div>
          <div><i>    ecutwfc =50</i></div>
          <div><i>    vdw_corr='DFT-D',</i></div>
          <div><i> !   lspinorb=.true.</i></div>
          <div><i> !   noncolin=.true.</i></div>
          <div><i> !   ecutrho=300</i></div>
          <div><i> !   nbnd=14</i></div>
          <div><i>!    occupations='smearing'</i></div>
          <div><i>!    smearing='gaussian'</i></div>
          <div><i>!   degauss=0.01</i></div>
          <div><i> !  nspin=2</i></div>
          <div><i> !   starting_magnetization(1)=0.1</i></div>
          <div><i>! Hf  95.94  Hf.pbe-mt_fhi.UPF</i></div>
          <div><i>! S  32.065  S.pbe-mt_fhi.UPF</i></div>
          <div><i>/</i></div>
          <div><i> &electrons</i></div>
          <div><i>    electron_dynamics='verlet'</i></div>
          <div><i>    electron_velocities='zero'</i></div>
          <div><i>    emass=400</i></div>
          <div><i>    emass_cutoff=1</i></div>
          <div><i>/</i></div>
          <div><i> &ions</i></div>
          <div><i>    ion_dynamics = 'verlet'</i></div>
          <div><i>    ion_damping=0.1</i></div>
          <div><i>    tempw=300</i></div>
          <div><i>    fnosep=6</i></div>
          <div><i>!    ion_nstepe=10</i></div>
          <div><i> /</i></div>
          <div><i> &cell</i></div>
          <div><i>    cell_dynamics = 'pr'</i></div>
          <div><i> </i></div>
          <div><i>/</i></div>
          <div><i>ATOMIC_SPECIES</i></div>
          <div><i> Hf  95.94  Hf.pbe-mt_fhi.UPF</i></div>
          <div><i> S  32.065  S.pbe-mt_fhi.UPF</i></div>
          <div><i>ATOMIC_POSITIONS angstrom</i></div>
          <div><i>   Hf    0.0000000000    0.0000000000    0.0000000000</i></div>
          <div><i>   S    1.8264500020    1.0545013980    1.4545075260</i></div>
          <div><i>   S   -0.0000000020    2.1090027990   -1.4545075260</i></div>
          <div><i>   Hf    0.0000000000    0.0000000000    5.6544000000</i></div>
          <div><i>   S    1.8264500020    1.0545013980    7.1089075260</i></div>
          <div><i>   S   -0.0000000020    2.1090027990    4.1998924740</i></div>
          <div><i>   Hf   -1.8264500000    3.1635041980    0.0000000000</i></div>
          <div><i>   S    0.0000000020    4.2180055960    1.4545075260</i></div>
          <div><i>   S   -1.8264500020    5.2725069970   -1.4545075260</i></div>
          <div><i>   Hf   -1.8264500000    3.1635041980    5.6544000000</i></div>
          <div><i>   S    0.0000000020    4.2180055960    7.1089075260</i></div>
          <div><i>   S   -1.8264500020    5.2725069970    4.1998924740</i></div>
          <div><i>   Hf    3.6529000000    0.0000000000    0.0000000000</i></div>
          <div><i>   S    5.4793500020    1.0545013980    1.4545075260</i></div>
          <div><i>   S    3.6528999980    2.1090027990   -1.4545075260</i></div>
          <div><i>   Hf    3.6529000000    0.0000000000    5.6544000000</i></div>
          <div><i>   S    5.4793500020    1.0545013980    7.1089075260</i></div>
          <div><i>   S    3.6528999980    2.1090027990    4.1998924740</i></div>
          <div><i>   Hf    1.8264500000    3.1635041980    0.0000000000</i></div>
          <div><i>   S    3.6529000020    4.2180055960    1.4545075260</i></div>
          <div><i>   S    1.8264499980    5.2725069970   -1.4545075260</i></div>
          <div><i>   Hf    1.8264500000    3.1635041980    5.6544000000</i></div>
          <div><i>   S    3.6529000020    4.2180055960    7.1089075260</i></div>
          <div><i>   S    1.8264499980    5.2725069970    4.1998924740 </i></div>
        </div>
        <div><br>
        </div>
        <div>Now the temperature is still oscillating around 80-90K
          after 50 ps simulation as if that is the desired temperature</div>
        <div><br>
        </div>
        <div><img src="cid:part1.004E02A0.658D9FA6@sissa.it" class=""
            width="481" height="288"></div>
        <div><br>
        </div>
        <div>And for a 3*3*3 supercell:</div>
        <div><br>
        </div>
        <div>
          <div><i>&control</i></div>
          <div><i>    calculation='vc-cp',</i></div>
          <div><i>    title='Halfnium disulfide'</i></div>
          <div><i>    restart_mode='restart',</i></div>
          <div><i>    ndr=52,</i></div>
          <div><i>    ndw=53,</i></div>
          <div><i>    nstep=1200000,</i></div>
          <div><i>    iprint=10</i></div>
          <div><i>    isave=100,</i></div>
          <div><i>    tstress = .true.</i></div>
          <div><i>    tprnfor = .true.</i></div>
          <div><i>    dt=10,</i></div>
          <div><i>    wf_collect=.true.</i></div>
          <div><i>    etot_conv_thr=1e-6</i></div>
          <div><i>    forc_conv_thr=1e-3</i></div>
          <div><i>    ekin_conv_thr=1e-5</i></div>
          <div><i>    prefix='HfS2',</i></div>
          <div><i>    pseudo_dir='/home/jpeng/HfS2/potential'</i></div>
          <div><i>    outdir='./tmp/',</i></div>
          <div><i> /</i></div>
          <div><i> &system</i></div>
          <div><i>    ibrav= 4,</i></div>
          <div><i>    a=10.9587</i></div>
          <div><i>   c=16.9632</i></div>
          <div><i>    nat=81, ntyp= 2,</i></div>
          <div><i>    ecutwfc =50</i></div>
          <div><i>    vdw_corr='DFT-D',</i></div>
          <div><i> !   lspinorb=.true.</i></div>
          <div><i> !   noncolin=.true.</i></div>
          <div><i> !   ecutrho=300</i></div>
          <div><i> !   nbnd=14</i></div>
          <div><i>!    occupations='smearing'</i></div>
          <div><i>!    smearing='gaussian'</i></div>
          <div><i>!   degauss=0.01</i></div>
          <div><i> !  nspin=2</i></div>
          <div><i> !   starting_magnetization(1)=0.1</i></div>
          <div><i>! Hf  95.94  Hf.pbe-mt_fhi.UPF</i></div>
          <div><i>! S  32.065  S.pbe-mt_fhi.UPF</i></div>
          <div><i>/</i></div>
          <div><i> &electrons</i></div>
          <div><i>    electron_dynamics='verlet'</i></div>
          <div><i>    electron_velocities='zero'</i></div>
          <div><i>    emass=400</i></div>
          <div><i>    emass_cutoff=1</i></div>
          <div><i>/</i></div>
          <div><i> &ions</i></div>
          <div><i>    ion_dynamics = 'verlet'</i></div>
          <div><i>    ion_damping=0.1</i></div>
          <div><i>    tempw=300</i></div>
          <div><i>    fnosep=6</i></div>
          <div><i>!    ion_nstepe=10</i></div>
          <div><i> /</i></div>
          <div><i> &cell</i></div>
          <div><i>    cell_dynamics = 'pr'</i></div>
          <div><i> </i></div>
          <div><i>/</i></div>
          <div><i>ATOMIC_SPECIES</i></div>
          <div><i> Hf  95.94  Hf.pbe-mt_fhi.UPF</i></div>
          <div><i> S  32.065  S.pbe-mt_fhi.UPF</i></div>
          <div><i>ATOMIC_POSITIONS angstrom</i></div>
          <div><i>Hf 0.0000000000 0.0000000000 0.0000000000</i></div>
          <div><i>S 1.8264500020 1.0545013980 1.4545075260</i></div>
          <div><i>S -0.0000000020 2.1090027990 -1.4545075260</i></div>
          <div><i>Hf 0.0000000000 0.0000000000 5.6544000000</i></div>
          <div><i>S 1.8264500020 1.0545013980 7.1089075260</i></div>
          <div><i>S -0.0000000020 2.1090027990 4.1998924740</i></div>
          <div><i>Hf 0.0000000000 0.0000000000 11.3088000000</i></div>
          <div><i>S 1.8264500020 1.0545013980 12.7633075260</i></div>
          <div><i>S -0.0000000020 2.1090027990 9.8542924740</i></div>
          <div><i>Hf -1.8264500000 3.1635041980 0.0000000000</i></div>
          <div><i>S 0.0000000020 4.2180055960 1.4545075260</i></div>
          <div><i>S -1.8264500020 5.2725069970 -1.4545075260</i></div>
          <div><i>Hf -1.8264500000 3.1635041980 5.6544000000</i></div>
          <div><i>S 0.0000000020 4.2180055960 7.1089075260</i></div>
          <div><i>S -1.8264500020 5.2725069970 4.1998924740</i></div>
          <div><i>Hf -1.8264500000 3.1635041980 11.3088000000</i></div>
          <div><i>S 0.0000000020 4.2180055960 12.7633075260</i></div>
          <div><i>S -1.8264500020 5.2725069970 9.8542924740</i></div>
          <div><i>Hf -3.6529000000 6.3270083960 0.0000000000</i></div>
          <div><i>S -1.8264499980 7.3815097940 1.4545075260</i></div>
          <div><i>S -3.6529000020 8.4360111950 -1.4545075260</i></div>
          <div><i>Hf -3.6529000000 6.3270083960 5.6544000000</i></div>
          <div><i>S -1.8264499980 7.3815097940 7.1089075260</i></div>
          <div><i>S -3.6529000020 8.4360111950 4.1998924740</i></div>
          <div><i>Hf -3.6529000000 6.3270083960 11.3088000000</i></div>
          <div><i>S -1.8264499980 7.3815097940 12.7633075260</i></div>
          <div><i>S -3.6529000020 8.4360111950 9.8542924740</i></div>
          <div><i>Hf 3.6529000000 0.0000000000 0.0000000000</i></div>
          <div><i>S 5.4793500020 1.0545013980 1.4545075260</i></div>
          <div><i>S 3.6528999980 2.1090027990 -1.4545075260</i></div>
          <div><i>Hf 3.6529000000 0.0000000000 5.6544000000</i></div>
          <div><i>S 5.4793500020 1.0545013980 7.1089075260</i></div>
          <div><i>S 3.6528999980 2.1090027990 4.1998924740</i></div>
          <div><i>Hf 3.6529000000 0.0000000000 11.3088000000</i></div>
          <div><i>S 5.4793500020 1.0545013980 12.7633075260</i></div>
          <div><i>S 3.6528999980 2.1090027990 9.8542924740</i></div>
          <div><i>Hf 1.8264500000 3.1635041980 0.0000000000</i></div>
          <div><i>S 3.6529000020 4.2180055960 1.4545075260</i></div>
          <div><i>S 1.8264499980 5.2725069970 -1.4545075260</i></div>
          <div><i>Hf 1.8264500000 3.1635041980 5.6544000000</i></div>
          <div><i>S 3.6529000020 4.2180055960 7.1089075260</i></div>
          <div><i>S 1.8264499980 5.2725069970 4.1998924740</i></div>
          <div><i>Hf 1.8264500000 3.1635041980 11.3088000000</i></div>
          <div><i>S 3.6529000020 4.2180055960 12.7633075260</i></div>
          <div><i>S 1.8264499980 5.2725069970 9.8542924740</i></div>
          <div><i>Hf 0.0000000000 6.3270083960 0.0000000000</i></div>
          <div><i>S 1.8264500020 7.3815097940 1.4545075260</i></div>
          <div><i>S -0.0000000020 8.4360111950 -1.4545075260</i></div>
          <div><i>Hf 0.0000000000 6.3270083960 5.6544000000</i></div>
          <div><i>S 1.8264500020 7.3815097940 7.1089075260</i></div>
          <div><i>S -0.0000000020 8.4360111950 4.1998924740</i></div>
          <div><i>Hf 0.0000000000 6.3270083960 11.3088000000</i></div>
          <div><i>S 1.8264500020 7.3815097940 12.7633075260</i></div>
          <div><i>S -0.0000000020 8.4360111950 9.8542924740</i></div>
          <div><i>Hf 7.3058000000 0.0000000000 0.0000000000</i></div>
          <div><i>S 9.1322500020 1.0545013980 1.4545075260</i></div>
          <div><i>S 7.3057999980 2.1090027990 -1.4545075260</i></div>
          <div><i>Hf 7.3058000000 0.0000000000 5.6544000000</i></div>
          <div><i>S 9.1322500020 1.0545013980 7.1089075260</i></div>
          <div><i>S 7.3057999980 2.1090027990 4.1998924740</i></div>
          <div><i>Hf 7.3058000000 0.0000000000 11.3088000000</i></div>
          <div><i>S 9.1322500020 1.0545013980 12.7633075260</i></div>
          <div><i>S 7.3057999980 2.1090027990 9.8542924740</i></div>
          <div><i>Hf 5.4793500000 3.1635041980 0.0000000000</i></div>
          <div><i>S 7.3058000020 4.2180055960 1.4545075260</i></div>
          <div><i>S 5.4793499980 5.2725069970 -1.4545075260</i></div>
          <div><i>Hf 5.4793500000 3.1635041980 5.6544000000</i></div>
          <div><i>S 7.3058000020 4.2180055960 7.1089075260</i></div>
          <div><i>S 5.4793499980 5.2725069970 4.1998924740</i></div>
          <div><i>Hf 5.4793500000 3.1635041980 11.3088000000</i></div>
          <div><i>S 7.3058000020 4.2180055960 12.7633075260</i></div>
          <div><i>S 5.4793499980 5.2725069970 9.8542924740</i></div>
          <div><i>Hf 3.6529000000 6.3270083960 0.0000000000</i></div>
          <div><i>S 5.4793500020 7.3815097940 1.4545075260</i></div>
          <div><i>S 3.6528999980 8.4360111950 -1.4545075260</i></div>
          <div><i>Hf 3.6529000000 6.3270083960 5.6544000000</i></div>
          <div><i>S 5.4793500020 7.3815097940 7.1089075260</i></div>
          <div><i>S 3.6528999980 8.4360111950 4.1998924740</i></div>
          <div><i>Hf 3.6529000000 6.3270083960 11.3088000000</i></div>
          <div><i>S 5.4793500020 7.3815097940 12.7633075260</i></div>
          <div><i>S 3.6528999980 8.4360111950 9.8542924740</i></div>
          <div><br>
          </div>
          The temperature never goes up to even 5K!</div>
        <div><br>
        </div>
        <div><img src="cid:part2.D2C12C37.EEA8ADAA@sissa.it" class=""
            width="480" height="288"><br>
          <br>
        </div>
        <div>And FYI, in the post I sent couple of days ago, I have
          already checked that cp relaxation calculation on 2*2*2 and
          3*3*3 supercell gives me an accurate description of the
          lattice structure.</div>
        <div><br>
        </div>
        <div>So below I write down some of my thought that lead to some
          questions:</div>
        <div><br>
        </div>
        <div>1. What determines the time spent on heating up my system?
          I can tell from the plots that for 2*2*2 it took maybe 2-3 ps
          to heat the system to around 80-90K while for 3*3*3 it took
          0.5ps to heat it to around 1K. But I am not sure which
          parameter controls the rate at which the temperature is being
          raised. I know it is difficult to determine, since your system
          size, thermal properties and the thermostat all come into
          play. But do you have a reference for me to check on this
          topic or according to your experience, what parameters
          dominate the process of raising temperature of a system.</div>
        <div><br>
        </div>
        <div>2. Instead of the desired 300K, both my systems stabilize
          at a temperature much lower. There seems to be a "barrier"
          stopping increase in temperature. Right now I do not have a
          clue on what is going on here, intuitive thinking would be the
          thermostat is not able to transfer kinetic energy to my
          system. The thermostat has a 
          <i
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:small;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">fnosep=6
          </i><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:small;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">which
            is about in the middle of the phonon spectrum of my system
            (around 0 to 11Thz) as suggested by the users guide. A
            possible explanation would be that the thermostat is
            injecting energy into the system too slowly that I can
            hardly see a temperature increase, while only on a
            nanosecond scale or even larger scale will it become
            prominent. </span></div>
        <div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:small;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><br>
          </span></div>
        <div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:small;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">Thank
            you very much! I am so grateful for your explanation
            provided!</span></div>
        <div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:small;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><br>
          </span></div>
        <div>Best</div>
        <div>Jie</div>
      </div>
      <div class="gmail_extra"><br>
        <div class="gmail_quote">On Sat, Apr 14, 2018 at 11:20 AM,
          Stefano de Gironcoli <span dir="ltr"><<a
              href="mailto:degironc@sissa.it" target="_blank"
              moz-do-not-send="true">degironc@sissa.it</a>></span>
          wrote:<br>
          <blockquote class="gmail_quote" style="margin:0 0 0
            .8ex;border-left:1px #ccc solid;padding-left:1ex">
            <div bgcolor="#FFFFFF" text="#000000">
              <p>Dear Jie Peng,</p>
              <p> suppose you were running a model harmonic system in 1
                dimension.</p>
              <p>  M a = - K x</p>
              <p> at fixed energy  E. <br>
              </p>
              <p> The kinetic energy would fluctuate harmonically
                between 0 (at maximum/minimum elongation) and E at the
                equilibrium distance .</p>
              <p> On average the Kinetic energy would be E/2 and its
                fluctuation some big fraction of E^2</p>
              <p> Something like sigma^2 = 1/T \int_0^T (E cos^2(2pi
                t/T) -E/2)^2 dt = E^2 1/T \int_0^T (cos(4pi t/T)/2)^2 dt
                = (E/2)^2 1/2pi \int_0^2pi cos^2(x) dx = (E/2)^2 / 2 <br>
              </p>
              <p>  or<br>
              </p>
              <p>  sigma =  1/sqrt(2) * E/2 = 1/sqrt(2) avg EKin<br>
              </p>
              <p>  with 1 degree of freedom the mean square fluctuation
                of the kinetic energy is 70% of its average !</p>
              <p>  you have 3 atoms in your cell hence 9 degrees of
                freedom. Assuming each contributes independently to the
                average this goes down by a factor 1/sqrt(9)=1/3</p>
              <p>  actually more likely just 1/sqrt(6) as the total
                momentum is conserved so only 6 modes at Gamma are
                actually excited...<br>
              </p>
              <p>  If you perform your simulation in a bigger supercell
                with more atoms (more degrees of freedom) the average
                will be more stable     ( proportionally to 
                1/sqrt(#deg.of.freedom-3 )  ... moreover the thermal
                excitations of vibrational modes will be sampled more
                faithfully.</p>
              <p>  best<br>
              </p>
              <p>stefano<br>
              </p>
              <div>
                <div class="h5"> <br>
                  <div class="m_-1246506486387623425moz-cite-prefix">On
                    13/04/2018 21:39, Jie Peng wrote:<br>
                  </div>
                </div>
              </div>
              <blockquote type="cite">
                <div>
                  <div class="h5">
                    <div dir="ltr">Dear all
                      <div><br>
                      </div>
                      <div>I have been running MD simulations on HfS2
                        using cp.x code in Quantum espresso. I start
                        from initial configuration obtained from pwscf
                        vc-relax, and relax the system using cp.x by
                        consecutive steps of: electron
                        relaxation->ionic relaxation->cell
                        relaxation. Then, I just directly start a NVE
                        simulation starting from the equilibrium
                        configuration. I expect the system to almost
                        stay stationary or the temperature should be
                        very small since I am allowing dynamics in a
                        system that is already in equilibrium. However,
                        what I see is a huge fluctuation in the <i>tmpp</i> output
                        of cp.x, as I attach a figure showing variation
                        of tmpp (Ionic temperature) with simulation time</div>
                      <div><img
                          src="cid:part4.E1476DBD.6E915C0D@sissa.it"
                          class="" width="481" height="288"></div>
                      <div><br>
                        I did this because it is suggested in the user
                        guide you should apply an initial displacement
                        to the atoms in your system after the relaxation
                        since otherwise there will not be any dynamics.
                        But what I see here is a large fluctuation of
                        the system temperature.</div>
                      <div><br>
                      </div>
                      <div>The thinking or questions here are</div>
                      <div><br>
                      </div>
                      <div>1.Does the tmpp represents the physical
                        temperature of the system here? I think it
                        should be since it is the temperature
                        corresponding to kinetic energy of the ions.</div>
                      <div><br>
                        2.It above point is true, why is the temperature
                        varying so fiercely? Am I setting incorrect
                        parameters, for instance the timestep or the
                        fictitious mass? But I took those from previous
                        simulation steps where I did the relaxation, and
                        they all worked well since they successfully
                        drived my system to equilibrium, satisfying the
                        convergence threshold on total energy, forces
                        acting on atoms, and the fictitious electron
                        kinetic energy. I am confused at this point.</div>
                      <div><br>
                      </div>
                      <div>The input file for NVE simulation is attached
                        here:</div>
                      <div><br>
                      </div>
                      <div>
                        <div><i>&control</i></div>
                        <div><i>    calculation='cp',</i></div>
                        <div><i>    title='Halfnium disulfide'</i></div>
                        <div><i>    restart_mode='restart',</i></div>
                        <div><i>    ndr=53,</i></div>
                        <div><i>    ndw=54,</i></div>
                        <div><i>    nstep=50000,</i></div>
                        <div><i>    iprint=10</i></div>
                        <div><i>    isave=100,</i></div>
                        <div><i>    tstress = .true.</i></div>
                        <div><i>    tprnfor = .true.</i></div>
                        <div><i>    dt=10,</i></div>
                        <div><i>    wf_collect=.true.</i></div>
                        <div><i>    etot_conv_thr=1e-6</i></div>
                        <div><i>    forc_conv_thr=1e-3</i></div>
                        <div><i>    ekin_conv_thr=1e-5</i></div>
                        <div><i>    prefix='HfS2',</i></div>
                        <div><i>    pseudo_dir='/home/jpeng/HfS2/<wbr>potential'</i></div>
                        <div><i>    outdir='./tmp/',</i></div>
                        <div><i> /</i></div>
                        <div><i> &system</i></div>
                        <div><i>    ibrav= 4,</i></div>
                        <div><i>    a=3.6529</i></div>
                        <div><i>   c=5.6544</i></div>
                        <div><i>    nat=  3, ntyp= 2,</i></div>
                        <div><i>    ecutwfc =50</i></div>
                        <div><i>    vdw_corr='DFT-D',</i></div>
                        <div><i> !   lspinorb=.true.</i></div>
                        <div><i> !   noncolin=.true.</i></div>
                        <div><i> !   ecutrho=300</i></div>
                        <div><i> !   nbnd=14</i></div>
                        <div><i>!    occupations='smearing'</i></div>
                        <div><i>!    smearing='gaussian'</i></div>
                        <div><i>!   degauss=0.01</i></div>
                        <div><i> !  nspin=2</i></div>
                        <div><i> !   starting_magnetization(1)=0.1</i></div>
                        <div><i>! Hf  95.94  Hf.pbe-mt_fhi.UPF</i></div>
                        <div><i>! S  32.065  S.pbe-mt_fhi.UPF</i></div>
                        <div><i>/</i></div>
                        <div><i> &electrons</i></div>
                        <div><i>    electron_dynamics='verlet'</i></div>
                        <div><i>    electron_velocities='zero'</i></div>
                        <div><i>    emass=400</i></div>
                        <div><i>    emass_cutoff=1</i></div>
                        <div><i>/</i></div>
                        <div><i> &ions</i></div>
                        <div><i>    ion_dynamics = 'verlet'</i></div>
                        <div><i>    ion_damping=0.1</i></div>
                        <div><i>!    ion_nstepe=10</i></div>
                        <div><i> /</i></div>
                        <div><i> &cell</i></div>
                        <div><i>    cell_dynamics = 'none'</i></div>
                        <div><i> </i></div>
                        <div><i>/</i></div>
                        <div><i>ATOMIC_SPECIES</i></div>
                        <div><i> Hf  95.94  Hf.pbe-mt_fhi.UPF</i></div>
                        <div><i> S  32.065  S.pbe-mt_fhi.UPF</i></div>
                        <div><i>ATOMIC_POSITIONS (crystal)</i></div>
                        <div><i>Hf      -0.000000000  -0.000000000 
                            -0.000000000</i></div>
                        <div><i>S        0.666666667   0.333333333 
                             0.257234636</i></div>
                        <div><i>S        0.333333333   0.666666667 
                            -0.257234636</i></div>
                        <div><br>
                        </div>
                        <div>Anyone could help me on it? Thank you very
                          much.</div>
                        <div><br>
                        </div>
                        <div>Best</div>
                        <div>Jie</div>
                        -- <br>
                        <div
                          class="m_-1246506486387623425gmail_signature">
                          <div dir="ltr">
                            <div>
                              <div style="font-size:12.8px">------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>------------------------------<br>
                                Jie Peng</div>
                              <div style="font-size:12.8px">PhD student<br>
                                2134 Glenn Martin Hall, Mechanical
                                Engineering, University of Maryland<br>
                                College Park, Maryland, USA<br>
                                Phone:(+1) 240-495-9445<br>
                              </div>
                              <div style="font-size:12.8px">Email: <a
                                  href="mailto:jiepeng@umd.edu"
                                  target="_blank" moz-do-not-send="true">jiepeng@umd.edu</a><br>
                              </div>
                            </div>
                            <div><br>
                            </div>
                          </div>
                        </div>
                      </div>
                    </div>
                    <br>
                    <fieldset
                      class="m_-1246506486387623425mimeAttachmentHeader"></fieldset>
                    <br>
                  </div>
                </div>
                <pre>______________________________<wbr>_________________
users mailing list
<a class="m_-1246506486387623425moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org" target="_blank" moz-do-not-send="true">users@lists.quantum-espresso.<wbr>org</a>
<a class="m_-1246506486387623425moz-txt-link-freetext" href="https://lists.quantum-espresso.org/mailman/listinfo/users" target="_blank" moz-do-not-send="true">https://lists.quantum-<wbr>espresso.org/mailman/listinfo/<wbr>users</a></pre>
              </blockquote>
              <br>
            </div>
          </blockquote>
        </div>
        <br>
        <br clear="all">
        <div><br>
        </div>
        -- <br>
        <div class="gmail_signature" data-smartmail="gmail_signature">
          <div dir="ltr">
            <div>
              <div style="font-size:12.8px">------------------------------------------------------------------------------------------------------------------------<br>
                Jie Peng</div>
              <div style="font-size:12.8px">PhD student<br>
                2134 Glenn Martin Hall, Mechanical Engineering,
                University of Maryland<br>
                College Park, Maryland, USA<br>
                Phone:(+1) 240-495-9445<br>
              </div>
              <div style="font-size:12.8px">Email: <a
                  href="mailto:jiepeng@umd.edu" target="_blank"
                  moz-do-not-send="true">jiepeng@umd.edu</a><br>
              </div>
            </div>
            <div><br>
            </div>
          </div>
        </div>
      </div>
    </blockquote>
    <br>
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